Electricity: motive power systems – Positional servo systems – 'reset' systems
Patent
1997-11-17
2000-03-14
Martin, David
Electricity: motive power systems
Positional servo systems
'reset' systems
318615, 318616, G05B 1136
Patent
active
060377364
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a control system of a motor for driving a machine tool, etc., and in particular to a control system for identifying control constants such as inertia and viscous friction coefficients.
TECHNICAL BACKGROUND
For example, control constant identification systems include: the rotation speed and calculates torque command integration amount and rotation speed change width, then performs an operation of (inertia)=(torque command integration amount)/(rotation speed change width) for finding inertia (see Japanese Patent Unexamined Publication No. Sho 61-88780); section, executes a speed loop under P control, and finds load inertia from the ratio between steady speed deviation in a state in which no load inertia exists and that in a state in which load inertia exists (see Japanese Patent Unexamined Publication No. Hei 6-70566); and current detection values or current command values for finding a current area and corrects an initial inertia assumption value from the current area calculation result, thereby finding inertia (see Japanese Patent Unexamined Publication No. Hei 4-325886).
However, conventional examples (1), (2), and (3) have a problem that inertia identification value errors or variations are large if viscous friction or Coulomb's friction exists. The following problems are also involved: Particularly in (1), commands are limited to those for changing the rotation speed at a given rate; in (2), the effect of disturbance is easily received because integration control is not performed; and in (3), inertia is found while fuzzy inference, etc., is used to repeat a correction so that the initial inertia assumption value approaches the actual inertia, thus resulting in large amounts of complicated operations.
DISCLOSURE OF THE INVENTION
It is an object of the invention to provide a control constant identification system that can solve the problem.
To solve the problems, according to the invention, there is provided a control constant identification system comprising: command Vref and actual motor speed Vfb and controlling motor speed; a model and outputting an estimated torque command Tref'; and between a value STref resulting from time integration of the torque command Tref output by the speed control section at a predetermined interval [a, b] and a value STref' resulting from time integration of the torque command Tref' output by the estimation section at the predetermined interval [a, b], characterized in that that the actual motor speed Vfb and motor speed Vfb' found by the estimation section become the same non-zero values at the time b.
According to the invention, the control constant control system can be provided which contains small inertia identification value errors and variations and moreover can find inertia by performing a small amount of very easy operations even if viscous friction, constant disturbance, and Coulomb's friction exist.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a principle diagram to explain the basic concept of the invention;
FIG. 2 is a block diagram to elaborate on the principle of the invention;
FIG. 3 is a block diagram to elaborate on the principle of the invention;
FIG. 4 is a block diagram of an embodiment of the invention;
FIGS. 5A-5F are speed command examples;
FIG. 6 is a block diagram to show the speed control section, the estimation section, and the identification section in FIG. 4 in detail; and
FIG. 7 is an operation example using an AC servo motor.
BEST MODE FOR CARRYING OUT THE INVENTION
First, the principle of the invention will be discussed, next an embodiment using a motor will be described specifically. FIG. 1 is a principle diagram to explain the basic concept of the invention. Numeral 1 is a speed control section and numeral 2 is an estimation section. PI control is programmed in the speed control section 1 and only inertia J is to be controlled. Likewise, PI control is also programmed in the estimation section 2 and only inertia J' is to be controlled. In FIG. 1, if speed Vfb in the speed control sectio
REFERENCES:
patent: 4851754 (1989-07-01), Sakamoto et al.
patent: 5073746 (1991-12-01), Sakamoto et al.
patent: 5091684 (1992-02-01), Iwashita
Nakamura Hiroshi
Tsuruta Kazuhiro
Kabushiki Kaisha Yaskawa Denki
Martin David
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